Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 430,618	$ 374,442	$ 315,442
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(38,538)	(9,787)	(1,087)
Change in fair value of derivatives	37	(228)	(187)
Amortization of interest rate lock agreements	1,952	1,952	1,952
Other	(350)	(1,632)	782
Other comprehensive (loss) income	(36,899)	(9,695)	1,460
Comprehensive income (loss)	$ 393,719	$ 364,747	$ 316,902